Continuing on anchoring and improvements on Nu's overall internal commands (#2635).
`move column` sub command has been turned into the command `move` since
we use it to move exclusively columns. Examples added as well.
Fixed it to carry along any anchor locations that might be in place if
table to be moved originates from other sources.
The extra newline character makes it hard to use nu as part of an
external processing pipeline, since the extra character could taint the
results. For example:
```
$ nu -c 'echo test | xxd'
00000000: 7465 7374 test
```
versus
```
nu -c 'echo test' | xxd
00000000: 7465 7374 0a test.
```
This commit extracts five new crates:
- nu-source, which contains the core source-code handling logic in Nu,
including Text, Span, and also the pretty.rs-based debug logic
- nu-parser, which is the parser and expander logic
- nu-protocol, which is the bulk of the types and basic conveniences
used by plugins
- nu-errors, which contains ShellError, ParseError and error handling
conveniences
- nu-textview, which is the textview plugin extracted into a crate
One of the major consequences of this refactor is that it's no longer
possible to `impl X for Spanned<Y>` outside of the `nu-source` crate, so
a lot of types became more concrete (Value became a concrete type
instead of Spanned<Value>, for example).
This also turned a number of inherent methods in the main nu crate into
plain functions (impl Value {} became a bunch of functions in the
`value` namespace in `crate::data::value`).
